Researchers Made Exploration to the Raw Materials and Firing Technology for Porcelain from the Xing Kiln in the Late Sixth Century
In the process of firing ceramics, the appearance, structure and properties of ceramics are determined by raw materials and firing technology, so the study of raw materials and firing technology of ancient ceramics has always been a very important archaeological science topic. The late 6th century AD was the period when white porcelain was created and burned in northern China, and Xing Kiln was an important kiln for producing white porcelain in northern China. After archaeological excavation, a large number of kilns in the late Northern Dynasty and celadon and early white porcelain were discovered, which provided important physical data for studying the origin of white porcelain and the porcelain-making technology in northern China. Recently, Lu Xiaoke, a senior engineer from Shanghai Institute of Ceramics, China Academy of Sciences, led a research team to systematically study the early white porcelain and celadon unearthed from the kiln site of Fuwulou in Neiqiu, Xing Kiln, and made new progress in the raw materials and firing technology of early porcelain making in Xing Kiln.
In the study, plasma inductively coupled mass spectrometry (ICP-MS) and thermoelectric ionization mass spectrometry (TIMS) were used to analyze the trace element content and strontium isotope characteristics of raw materials. The results show that the early Xing ware bodies can be divided into two categories based on the trace elements pattern, indicating two kinds of raw material were used for making porcelain. It further states that the Xing potters intentionally selected a higher-quality raw material distinct from that of celadon for the production of new ware, early white porcelain, containing generally lower levels of trace elements such as V, Cr, Ni, Nb, Ta, Zr, and Hf, which are closely related to the impurities of zircon and rutile. The Sr isotope mixing patterns analysis demonstrates that the early Xing ware glaze did not generally follow the recipe of wood ash mixing with body clay, but rather mixed with other glaze-making clays. Furthermore, there are discrepancies in Sr isotope compositions between early white porcelain and celadon glaze, suggesting that Xing potters attempted to improve the whiteness by modifying the glazing technology. The related achievements were published in Science of Conservation and Archaeology (2024,36(1),11-20). The first author and correspondent of this paper is senior engineer Lu Xiaoke.
The research team combined thermal expansion instrument, X-ray photoelectron spectroscopy and scanning electron microscope to reveal the differences in firing technology and technical characteristics between celadon and early white porcelain from the perspectives of firing temperature, firing atmosphere and microstructure. The results show that Xing porcelains were fired at high temperatures exceeding 1200 °Cand even reaching 1300 °C with a reducing flame, which is consistent with the characteristics of a dome kiln powered by fire wood during the late sixth century. The high firing temperature makes the glaze turn to be glassy, with a few bubbles and residual quartz particles, while the body demonstrates the presence of numerous mullite crystals. Among the early Xing porcelains, the firing temperature of early white porcelain is slightly lower than that of celadon, with mean values of 1242 °C and 1279°C, respectively. This deliberate variation in firing temperature is a result of the ingenious technological advancements made by ancient potters to reduce glaze accumulation and improve the whiteness of products.The explorations promote the emergence of white porcelainin the Xing kiln during the late Sui dynasty, thus established a new pattern known as the "southern blue and northern white" in the Chinese history, becoming an important milestone in the history of ceramic development in China. The related achievements were published in “Archaeometry” (https://doi.org/10.1111/arcm.12969, 2024). The first author of this paper is Zong Ruofei, a graduate student of Shanghai Institute of Silicate, and the correspondent is Lu Xiaoke, a senior engineer.
The above research work is supported by the National Natural Science Foundation and other projects.
LU Xiaoke
Shanghai Institute of Ceramics
E-mail: luxiaoke@mail.sic.ac.cn
Two-dimensional correspondence analysis diagram of trace elements in the early porcelain body of Xing kiln
1/Sr content of glaze of early porcelain in Xing kiln -87Sr/86Sr scatter diagram
Cross-section microstructure of typical samples in Xing kiln early wares
Kilns in the Late Northern Dynasties of Xing kiln
